Exercise stool



FIG. 1 is a front perspective view of an exercise stool showing my new design;

FIG. 2 is a top view thereof;

FIG. 3 is a bottom view thereof;

FIG. 4 is a side view thereof, the opposite side view being identical thereof;

FIG. 5 is a rear view thereof; and,

FIG. 6 is a front view thereof.

The broken lines shown in the drawings are for the purpose of illustrating portions of the exercise stool, which form no part of the claimed design. 

CLAIM The ornamental design for an exercise stool, as shown and described. 